On a Long Term Evolution (LTE) network, user equipments (UE) can communicate with each other by using voice over LTE (VoLTE). VoLTE is a type of voice service that is based on an LTE system and an Internet Protocol multimedia system (IMS) network.
When UEs are communicating with each other by using VoLTE, reliability of a voice service of the UEs is reduced if an exception occurs on a network side (the network side is a network between an evolved NodeB (eNodeB) and a packet data network gateway (PGW) of an LTE system. For example, if a network between a serving gateway (SGW) and the PGW is interrupted, the ongoing voice service between the UEs is interrupted. Consequently, reliability of the voice service of the UEs is reduced.
Therefore, how to improve reliability of a voice service of UE is an urgent problem to be resolved by a person in the art.